One day this guard stopped a worker who was walking out of the factory gates pushing a wheelbarrow with a suspicious looking package in it.

The guard opened the package up and found it contained nothing but some old bits of rubbish, sawdust and floor-sweepings.

The next day he stopped the same worker who was again pushing a wheelbarrow containing a suspicious looking package. Once more it contained nothing of value.

The same thing happened many days on the trot, until the guard finally said, "OK, I give up. I know you are up to something, but I just can’t tell what. Please, I promise not to arrest you, but put me out of my misery - tell me what you are stealing."